This invention generally relates to polymerized filaments. More particularly, the present invention relates to polymerized liquid crystalline filaments. Specifically, the present invention relates to polymerized liquid crystalline filaments formed when a liquid crystalline solution undergoes a phase transition from the isotropic phase to the smectic phase. The present invention also relates to a method of polymerizing filaments.
Many liquid crystals undergo a phase transition from the isotropic phase to the smectic phase, a phase where the molecules are orientationally ordered and arranged in layers. Cooling a liquid crystalline solution in an isotropic phase induces a transition into the smectic phase, usually in the form of batonnettes, which are small compact regions of the smectic phase. Upon further cooling, these batonnettes grow and, upon entering the smectic A phase, coalesce to form a focal conic structure.
In some systems of solute and solvent and in a narrow temperature range, instead of batonnettes, a filament of material in the smectic phase is observed to emerge from the isotropic phase. This filament typically grows by elongating everywherexe2x80x94not only at the endsxe2x80x94while retaining substantially uniform thickness. As a result, the internal structure of the filament is concentric cylindrical layers of molecules around an axial isotropic core, making it highly ordered outside the core and substantially defect-free.
Defects are points or lines of diminished order. More specifically, they are the sites of abrupt change in the direction of the director of the liquid crystals. Almost always.
The lack of defects in liquid crystalline filaments, however, give the filaments highly desirable mechanical and optical properties. These properties are expected because highly ordered crystalline structures generally have high mechanical strength and minimal or no light scattering. Therefore, potential applications for these filaments include high strength fibers and textiles, optical wave guides and microelectronics.
Heretofore, no one has been able to take commercial advantage of these filaments because they are so concentration-and temperature-sensitive that they are usually short-lived, generally lasting only a couple hours in solution before either dissolving or collapsing into a globular structure. Therefore, there is a need for a liquid crystalline composition that forms filaments that can be preserved for a useful period of time.
It is therefore an object of the present invention to provide a compound that is capable of forming liquid crystalline filaments and is polymerizable.
It is another object of the present invention to provide a polymerized filament with an internal structure that is ordered and substantially defect-free.
It is a further object of the present invention to provide polymerized filaments with highly desirable mechanical and optical properties.
It is yet a further object of the present invention to provide a method of making polymerized filaments.
It is still yet a further object of the present invention to provide a method of making fibers from polymerized filaments.
At least one or more of the foregoing objects, together with the advantages thereof over the known art relating to polymerizable filaments, which shall become apparent from the specification which follows, are accomplished by the invention as hereinafter described and claimed.
In general, the present invention provides a polymerizable liquid crystalline monomer comprising a polymerizable first terminal group, a central portion, and a second terminal group, wherein the liquid crystalline monomer can be defined by formula (I): 
where R1 is a vinyl group or an epoxide, R2 and R4 are each independently selected from hydrogen or organic groups containing from 1 to about 20 carbon atoms; R5 is a cyclohexyl or an aromatic group, preferably biphenyl, phenylcyclohexyl, cyclohexylcyclohexyl, phenylbenzoate, biphenylbenzoate, or phenylpyrimidine; R6 is a polar group containing from 0 to about 18 carbon atoms and may contain one or more double bonds; and R3 is either a bond, xe2x80x94CHxe2x95x90CHxe2x80x94, benzene, oxygen, sulfur, nitrogen, carboxylate, or 
where Y is hydrogen or a lower alkyl group having from 1 to about 8 carbon atoms; and wherein the monomer is capable of filament formation.
The present invention also includes a method of making a polymerized liquid crystal filament comprising providing a polymerizable liquid crystal monomer, mixing the monomer with a solvent such that the resulting solution exhibits separation from an isotropic phase to a smectic phase and the interfacial energy between the isotropic phase and the smectic phase has a negative anisotropy, inducing filament formation, and polymerizing the filament.